1. Field of the Invention
This invention relates to a multistage speed change gear system for transmitting rotary motive force from the drive side to the driven side by changing speed at least in two stages.
The multistage speed change gear system according to the present invention is suitable for use as speed increasing gearing or speed reducing gearing for various types of compressors and blowers. The compressors and blowers include those which are for use with refrigerating apparatus.
2. Description of the Prior Art
Japanese Pat. Kokai (Laid-Open) No. 140014/77 shows a conventional multistage speed change gear system, which will be described by referring to FIG. 1. As shown, the multistage speed change gear system comprises a gear box 1, a low speed shaft 4 journalled by bearings 2 and 3 fitted to the gear box 1, two gears 7 and 8 journalled by bearings 5 and 6 respectively fitted to the low speed shaft 4, a high speed shaft 13 having fitted thereto pinions 9 and 10 meshing with the gears 7 and 8 respectively, two bearings 11 and 12 fitted to the gear box 1 for supporting the high speed shaft 13, a click clutch 14 for connecting one of the gears 7 and 8 to the low speed shaft 4, and a shifter 15 for operating the dog clutch 14.
In this type of speed change gear system, the gears 7 and 8 are in alignment at their centers with the center axis of the low speed shaft 4, and the gears 7 and 8 are in direct meshing engagement with the pinions 9 and 10 respectively without using idle gears. The system offers the advantage of enabling a compact overall size to be obtained in a multistage speed change gear system in spite of its speed change ratio being high. However, in this system, the low speed shaft 4 is connected to the gear 7 or 8 to transmit rotary motive force by way of low speed shaft 4.fwdarw.dog clutch 14.fwdarw.gear 7 (or gear 8).fwdarw.pinion 9 (or pinion 10).fwdarw.high speed shaft 13. In this condition, the relative speed between the gear 7 (or gear 8) and the low speed shaft 4 engaged in transmission of rotary motive force becomes zero, the balls or rollers of the bearing 5 (or bearing 6) remain stationary between inner and outer races of the bearing 5 (or bearing 6). When the bearings 5 and 6 are ball bearings, the inner and outer races are brought into point contact with each ball; when they are roller bearings, the inner and outer races are brought into line contact with each roller. In this condition, the load transmitted by the meshing engagement of the gear 7 with the pinion 9 or of the gear 8 with the pinion 10 acts between each race and each ball (or roller) of the bearings 5 and 6, and very small vibration produced by the rotation of the shaft system is transmitted to the bearings 5 and 6. Therefore, each ball or roller of the bearings 5 and 6 will rub against the inner and outer races thereof at one point only or along one line only at all times, thereby producing fretting corrosion in the bearings 5 and 6.